The taillights and interior dome light are on the same circuit...the brake lights are on a different circuit, but the two wires for taillights and brake lights run Parallel,,.. and they both use different sides of the same bulb..... somewhere either the wires have rubbed off the insulation, and are shorting....or you have a bad bulb holder in one of your taillights... or you have a bad bulb....I would start there, and work my way back....
Happy Hunting.....
